I was comparing the Modulation Transfer Function (MTF) charts of the three Sony 'G' lenses against the Canon lenses of the same focal length, and from what I see, Sony's 'G' lenses does as well, if not better that the Canon lenses.

Comparing the Sony 300mm f/2.8 G lens against the Canon 300mm f/2.8 IS HSM, shows that based on the MTF chart, the Sony is a better lens. Both lenses had the same performance at the center of the lens, but the Sony showed better performance as you got further away from the center.

The Sony 70-200mm f/2.8 G also did very well against the Canon 70-200mm f/2.8 IS. The MTF was better for Sony except at 200mm where the Canon does show better performance at the edges.

The results for the Sony 35mm f/1.4 G against the Canon 35mm f/1.4 L was a little more of a tie, as the Sony did better at F/8, but not as well at f/1.4.

The MTF charts were supplied by the manufacturer.